This invention relates to a scanner for reading indicia such as bar codes. When used herein "reading indicia" means extracting information from indicia, as in determining the presence and width of black bars and white spaces in reading bar code. More particularly it relates to a scanner for reading indicia such as bar codes, where the illumination level of the light source is maintained at a low value when the scanner is not reading indicia and is modified to a high level when indicia are to be read, the change in illumination level being precipitated by exposure of the scanner to a surface of relatively high reflectivity.